Accessory Dwelling Unit (ADU) City Regulations
Number of ADUs allowed:
One ADU is allowed per legal, residential lot of record.
Types of ADUs allowed:
Only conversions of existing interior space are the only type of ADU that is allowed by right. Though opportunities for detached units and additions still exist, in San Francisco, the vast majority of properties which could add an ADU, are able to do so through the conversion of existing space.
The minimum build-able lot size is 2,500 square feet. Smaller lots are subject to approval for development through the variance process.
San Francisco currently has only one zoning designation that specifically regulates New Construction Detached/Attached secondary units - ADUs in RH-1(S) zones are limited to 600 square feet. In other residential zones, there are no limits placed on the size of new dwelling units, though they must be created within the existing space available.
Front, side and rear lot line setbacks are determined by those of the zoning district. One important item to note is that in almost no case will it be allowed to build an addition or new structure in the last 25% (or 15’ at minimum) of your property (for example, if your lot is 100’ deep, the rear setback would be 25’ from the back property line). The rear yard requirement can be up to 45% of the overall depth of your lot, depending on zoning.
While the Planning Code requires one parking space per residential unit in most neighborhoods, Section 150(c) states that additional parking is only required for renovations that increase the overall required parking count by two or more spaces. Adding a single ADU would not require an additional parking space anywhere in the City. Sections 150(e) and 161 allow for the reduction of car parking spaces on site if they are replaced with Class 1 bicycle spaces (indoor, secure and sheltered). You may be required to add bicycle parking for the ADU as well. *** New statewide standards provide for exemptions to these parking requirements if the property is within 0.5 mile walking distance to a public transport station.
Fire sprinklers are an example of active fire protection, and are now required in all new single family residential construction in California. In the case of adding an ADU to an existing single-family home, you will most likely only be required to add sprinklers to the new unit, adjacent spaces on the same floor, and along the exit path - unless directed otherwise at your pre-application meeting.
Smoke and CO Detectors Smoke alarms are required to be installed in all new dwelling units. These items must be hard-wired into the building’s electrical system.
Fire separation will be required between the ADU and any adjacent garage or property line and between any living space above.
Shape, materials and style:
Exterior modifications will be required to resemble those of the primary structure. Interior conversions of existing space are not subject to this requirement.
Ceiling heights within the dwelling unit are governed by the Building Code as well. The main living space and the bedroom must have 7’-6” minimum ceiling heights. The other rooms in the unit - kitchen, bathroom, hallways, laundry rooms - can have ceilings as low as 7’-0”. Headroom is typically quite low when dealing with adding ground floor units to hillside properties, or in existing garages - and there are a number of exceptions for beams and sloped or furred
ceilings - so clearances should be should be reviewed during the pre-application meeting.
Reference 2013 SFBC/CBC Section 1208
It was a discretionary review process, but is now updated in 2018 to comply with State Law. California now requires that ADUs be approved through a ministerial process or "by right".
Minimum Room and Unit Sizes
The main living space and the bedroom must each be at least 7’ wide. There is no minimum room size for kitchens, but you must provide at least 36” of clear floor space in front of cabinets and appliances. Reference 2013
SFBC/CBC Section 1208.
Every dwelling unit must have at least one room that provides at least 120 square feet
of net habitable floor area. Other habitable rooms - bedrooms and living rooms, but not
kitchens, bathrooms, or storage rooms - must have at least 70 square feet of net floor area.
Reference 2013 SFBC/CBC Section 1208
Efficiency Dwelling Units: The Building Code has a specific category for an exceptionally small studio unit that has one room used for sleeping, cooking, eating, and living. The total area of the unit (including bathroom, closets, kitchen, and all living and sleeping space) must be at least 220 square feet. The unit is limited to two occupants. An additional 100 square feet of unit area must be provided for each occupant over this two-person limit. The primary living space (the area of the unit excluding the closet and bathroom) must at least 150 square feet. In addition to the size requirements, Efficiency Units must contain the following:
• a separate closet
• a kitchen with a sink, refrigerator, and cooking appliance; with at least 30” clear floor space in front of the counter and appliances
• a bathroom with a toilet and sink, and a bathtub or shower
• the same light and ventilation as required for other dwelling types
Reference 2013 SFBC/CBC Section 1208.
Unit is not intended for sale separate from the primary residence and may be rented. (State requirements)
One of the advantages to constructing an ADU within an existing building rather than as a detached, free-standing structure is that the water and drain lines are usually (relatively) easy to tap into so that the services can be extended to the new unit’s bathroom and kitchen.
ADUs do require their own electrical service, with a dedicated electrical meter, circuit panel, and shut-off.
Historic Resource Determination
Most buildings in San Francisco that are 50 years and older that have not had an historic survey completed are classified as Category B resources, meaning that they are of potential importance. If your project involves alteration to a structure that has been identified (through a Historic Resource Determination Survey or other means) as a historic resource, or if the structure is 50 years old or greater, then there will most likely be additional materials and process involved in order to determine if the proposed work is appropriate. However, if your project is entirely within the existing structure and doesn’t involve changes to the front of the building, you will most likely not be affected by historic preservation guidelines.
All Single Family Zones (RH-1, RH-1(D), RH-1(S)). Multifamily parcels which are under the maximum allowable density of the zone may also be eligible. (RH-2, RH-3, RM-2, RM-3, RM-4.)
Street Curb Cuts
If you are removing a garage as part of adding an ADU, the Department of Public Works (DPW) will require that you also remove the curb cut that used to provide driveway access to that garage.
Street Trees & Front Yard Improvements
The Planning Department requires one street tree along the sidewalk of a typical 25’ wide residential lot. Adding a unit or legalizing a unit may trigger this requirement. If the property does not already have a street tree in place, one may need to be provided as part of the permit requirements. Reference SF Planning Code Section 138. Similarly, the Planning Code has requirements for landscaping and permeability in the front yard set back of most residential zoning districts. These are likely to be required as part of the Planning Department’s review of the project. Reference San Francisco Green Landscaping Ordinance, and the SF Planning Code Section 132
Note that many of San Francisco's requirements for ADUs are out of compliance with the State of California's mandate legislation. The city expects to update its ADU ordinance to comply in 2018. Particular areas to note are parking requirements and review process which will need to be updated to comply.
2015 SF ADU Guidebook (Will be updated 2018)
Rescue openings must be provided from every sleeping room in a dwelling - this means each bedroom needs to have its own rescue opening. In the case of a studio apartment, the main living space needs a window or door that complies with the rescue opening requirement. If it is a window, it must be at least 5.7 square feet in size (5’ at the ground floor). The net opening can’t be less than 24 inches high or 20 inches wide, and the bottom can’t be more than 44 inches above the floor. It also needs to open freely to allow a person to climb out, meaning it can’t require any keys or tools to open. A door that leads to a public way or to a court that opens to a public way also meets the requirement. Reference 2013 SFBC/CBC Section 1029.
San Francisco has a neighbor notification process for building projects that meet certain criteria in Planning Code Section 311 and 312. This means everyone who lives within a certain radius of your property needs to be notified of the project and has an opportunity to file for a Discretionary Review, which is an opportunity for neighbors to express their concerns and provide input early in the project. There is also a pre application neighborhood meeting required. Adding an ADU does not automaticaly trigger Neighborhood Notification. If your project is built entirely within the existing footprint of the building, you will not have to go through this process.
Prior to doing detailed design of your ADU project, it is possible to schedule an Pre-Application meeting with the Department of Building Inspection, and if necessary, the San Francisco Fire Department (for buildings with three or more units). The Pre-Application meeting is a chance to obtain feedback that can clarify many critical code issues. There is a fee to set up this meeting, but it can save a lot of time and money later in the construction process. Questions are submitted in advance of the meeting, and notes taken during the meeting of agreed-upon interpretations are sent back to the officials for review and their signatures. The written record becomes part of your building permit application.
DPW also enforces a San Francisco municipal code that requires garbage, recycling, and compost receptacles to be stored so that they are not visible from the street. In planning for an ADU that may take up a substantial amount of the garage space, care should be taken to maintain adequate space for the receptacles, or to provide a screened outdoor area where they may be stored. Information on acceptable screening enclosures can be found by searching for ‘Garbage and Recycling Receptacles’ at the Department of Public Works’ website: www.sfdpw.org.
For more ADU Information